Change speed transmission for vehicles



July 30, 1957 w. o. BECHMAN Erm. 2,800,803

' CHANGE SPEED TRANSMISSION FOR VEHICLES Original Filed' June 10, 1948 nii-ed States Patent CHANGE SPEED TRANSMISSION FR VEHICLES William Becliman and Nicholas J. Palkovic, Chicago, Ill., assignors to International Harvester Company, a corporation of New Jersey Original application .lune 10, 1948, Serial No. 32,118, now Patent No. 2,661,634, dated December 8, 1953. giiizlg and this application April 7, 1953, Serial No.

4 Claims. (Cl. 74-411) .This invention has to do with change-speed transmission apparatus wherein power is selectively transmitted either through or independently of an auxiliary speed changing power transmission unit to and through a principal change-speed power transmission unit to final drive mechanism of vehicles, and more particularly concerns such an auxiliary transmission unit having concentric shafts through one of which power is receivable from a driving structure common to said units and then transmitted at a different speed through the other of said shafts to the principal change-speed unit. This application is a division of our copending application Serial No. 32,118, filed .lune 10, 1948 for Change-Speed Transmisison For Vehicles, now Patent No. 2,661,634.

Power transmission apparatus constructed according to the present invention is particularly adapted for use upon vehicles such as crawler tractors which are propelled and steered by driving propelling units at opposite sides of the vehicle at the same or different speeds. Vehicles of this kind comprise a final drive housing wherein there is a final drive mechanism including coaxial final drive shafts extending oppositely from a fore and aft center line position of the vehicle toward opposite sides thereof for respective drive connection with the propelling units at the opposite sides of the vehicle. Such vehicles conventionally comprise a change-speed power transmission unit forwardly of the final drive casing and having a driven shaft driving connected with the two oppositely extending coaxial final drive shafts in such casing. The changespeed transmission unit conventionally includes a main shaftwhereon there are gears respectively mated with gears upon a countershaft for driving this countershaft at different speed reductions, and this countershaft constitutes the driven shaft having the driving connection with the final drive mechanism. When the main shaft of the change-speed transmission unit is made tubular and a drive shaft structure projects endwise through the tubular shaft, it is possible to drive the tubular main shaft through a driving connection with a forward end of the drive shaft structure or to alternatively drive the tubular driven shaft through a driving connection with therear end of the drive shaft structure.

A general object of this invention is the provision of an auxiliary power transmission operable between the rear ends of the concentric shaft and shaft structure to transmit driving force to the tubular shaft at a speed different than that of the drive shaft structure.

A further object is the provision of an auxiliary power transmission unit of the aforesaid character that includes gears respectively constrained for rotation with rear end portions of the drive shaft structure and of the tubular driven shaft, and also includes a countershaft structure comprising gears respectively meshed with the first named gears, and said gears being of a diameter ratio to provide a very slow creeping speed for the vehicle.

The above and other desirable objects inherent in and encompassed by the invention will be readily compre- Patented July 30, 1957 hended from the ensuing description and claims together with the annexed drawings, wherein:

Fig. 1 is a vertical sectional view taken axially through power transmission apparatus embodying a preferred form of the invention and taken centrally and transversely through final drive mechanism of a Steering-by-driving vehicle.

Fig. 2 is a fragmentary transverse sectional view taken on the line 2-2 of Fig. 1 illustrating transmisison controls and an interlock device therefor.

Fig. 3 is a fragmentary plan view showing details of a slip clutch employed in the auxiliary power transmission unit constituting the left-hand portion of Fig. 1 and taken on the line 3-3 of Fig. l.

Fig. 4 is a fragmentary plan view taken on the line 4-4 of Fig. 1 and illustrating a portion of a shifter fork control for the auxiliary power transmission unit.

The power transmission apparatus herein shown is for driving final drive mechanism 11 contained within a final drive housing 12. A rear wall of this housing is designated 13 and a front wall thereof is designated 14. The final drive mechanism includes a conventional large bevel gear 15 driven by a pinion 16 formed upon the rear end of a splined countershaft 17 of a change-speed power transmission unit 18 which includes a gear box 19 projecting forwardly from the front wall 14 of the final drive casing. Bevel gear 15 is arranged coaxially with oppositely extending final drive shafts 21 of which one is shown in Fig. 1. These final drive shafts 21 are drivingly connected with propelling and steering units, such as endless tr eads of crawler tractors, by conventional power transmitting connections which are thought unnecessary to show in conjunction with the disclosure of the present invention:

Normally the final drive mechanism will be driven by power transmitted solely through the change-speed transmission unit 18, but when it is desired to drive this mechanism, and hence the vehicle at an ultra-slow speed, an auxiliary power transmission unit 22, which is mounted lon the rear wall of the final drive casing 12, will be used in combination with certain parts of the change-speed transmission unit 18. n

Referring now to the change-speed transmission lunit 18, it includes a main drive shaft 25 journaled within bearing units 26 and 27 in the front wall 2S `of the -gear box. This main drive shaft has a gear 29 formed integrally with its inner end and also comprises an internally splined recess 31 for meshing with splines upon the -front end of a long shaft 32 which is disposed concentrically within an externally splined tubular shaft 33. Inasmuch as the long shaft 32 is constrained for rotation with the main drive shaft 25, said shafts 25 and 32 may be collectively regarded as a drive shaft structure 25-32. The externally splined tubular shaft 33 is rotatively carried at its forward end in a bearing unit 34 within a recessed end of the main drive shaft gear 29 and is rotatively carried at its rear end within a ball bearing unit 35 carried by the wall 14 which divides the final drive casing from the gear box and therefore constitutes the forward wall of the final drive casing and the rear wall of the gear box.

A gear 36 splined to the tubular drive shaft 33 carries internal clutch teeth comprising one counterpart 37 of a jaw clutch 37-38 of which the companion component 38 consists of clutch teeth integral with the teeth of the gear 29. When the gear 36 occupies its most forward position wherein the teeth 37 are meshed with the teeth 38, the main drive shaft 25 is directly connected with the tubular diive shaft 33. Under these circumstances the change-speed transmission unit will be connected in its high speed range and the countershaft 17 can be driven at different speeds when the drive shaft gears 41, 42, and 43 are respectively meshed with countershaft gears 44,

- a;soo,sos e f 45, or 46. The gears 41 and 42 are part of a gear cluster splined to the shaft 33 and movable axially thereof by a shifter fork (not shown) cooperable with a shifter fork groove 47. `,The;gear:43;which is-'splinedto rt'hefshaft; is shiftable to and frommeshed-'relation wi-ththe gearr46 by .-ashifterffork (notfshown) ACooperable with a shifter fork groovei48. Gear 43is shownainpaV rneutral position axiallygof/the shaft 33 and may -be.slid.rearwardly,ithat is, to thelleft as viewed in Fig. 1,-into meshawith.. one gear of a reversing gear cluster (not shown) of whichffa secondgear of the cluster meshes with. countershaft.l gear 49 -to cause Areverse drive of thecountershaft .17. :This reversing drive for the countershaft isconventionalfwherefore it -is not illustrated inthe drawings .An alternative driving. connection between ,the gmain drive shaft 25 and thetubular` drive,shaft 33,. employable instead of the clutch 37-38, Vcomprisesa pairof .diagrannnaticallyillustrated Vgears ,51,.and-52 .which fare respectively meshed with the gear 29andthe slidable .gear 36 when the latter is in its rearmost position illustrated inFig,.l. The gears 51 and 52are elements of algear cluster 51-52 journaled upon a rod'53supported at its ends in suitable parts-of the gear box. .When Vthe Agear 36 occupies a neutral `position between the position illustrated in Fig. l and its foremostl position wherein the clutch 37.-38is engaged, such gear will'be demeshed from the gear 52 and the clutch V37-f33 will be disengaged, permitting the main drive shaft.25Y to rotate Without transmitting power to any of the gears mounted upon lthe tubular drive shaft 3.3.

Normally the countershaftl 17, and hencethe final drive shafts 21 of the 'final drive mechanism, will'be -driven through gear trains including `the various meshable `gears upon the .tubular drive shaft 33 and the courltershaft=to gether with a driving connection through thejclutch 37-538 or through the gears 29-51-52-36. However, when it is desired to drive the final drive shafts 21-at-extremely slow speeds, the transmission unit 22 on the rear-wa`l1uof the final drive casing will be 'employed in"lieu"ofsaid clutch 37-38 or the low speed connection including the gear chain 29-51-52-36. Thisauxiliarytransmission unit `constitutes an alternate yspeed reduction means for driving the tubular drive shaft 33 from the mainedrive shaft structure 25-32. When vthe tubular :shaft133 is driven at the extremely slow speeds lpossible thr011gh;the auxiliary transmission unit, the countershaft 17..an`d,.the final drive shafts 21 will be driven .at correspondingly extremely slow speeds which are selectable by ,selective meshing of the gear pairs 41-44, 42-45, landA-gslt. It is also possible to drive the vehicle in reverse at ian extremely slow speed using the auxiliary transmission unit when the reversing gearg43 is shifted rearwardly Yfrom the neutral position shown in Fig. 1 for'conneetingg'the reversing gear cluster (not shown) in seriesfbetweennthis gear 43 and the countershaft reversing gear 49.

Auxiliary transmission unit 22 includes a separate casing 55 detachably secured to the nal drive casing rearwall 13 by a plurality of stud bolts 56, of which one isshown in Fig. l, and nuts 57 on these-bolts. An-opening'SSin the forward wall '59 of the auxiliary transmission unit casing contains a ball bearing unit`61 which yregistersiwith an opening 62' in the final drive casing rear wall 13. Casing bearing units 61 and 62 providea journal `support for a tubular driven shaft 63 Vwhich extendsforwardly from the auxiliary transmission unit into driving relation with the tubular transmission shaft 33 -by means lof xan internally splined coupling sleeve v64 of which'the-splines mesh with splines 65 and 66, respectively, ,'uponthe rear end of the tubular shaft 33.1and upon the forward end-of the tubular shaft p63. The long drive shaft32 is .arranged concentrically within'the tubular driven shaft'63 andj'has a journal support on a rear endportion thereof ball bearing units 67 and 68 .mounted withintheauxiliary transmission casing 55. A vgear .69 ris formed integrally with the rear end of the drive shaft 32, whereas a considerably larger diameter gear 71 is splined at 72 to a rear end portion of the tubular driven shaft 63. Gear 69 is meshed with a gear 73 of a countershaft structure whereas the gear 71 ismeshed" with a gear 74 of the countershaft structure. A slip clutch 75, comprising elements 76 Vand 77 respectively -upon a--hub Iof the gear 73 and splined at 78 toa shaft'element 79 of the countershaft structure, constitutes a means for limiting the amount of torque transrnittable from' the 4gear '7.3 .to the .shaft element. A jaw clutch V81 constitutes means for establishing or disestablishing a driving connectionbetween the shaft element 79 and 'the countershaft gear 74. Jaw clutch 81 comprises an externally splined hubxtension 82 of the gear 74, clutch teeth 83 on the shaft element 79, and an internallypplined collar 84 axially slidable from the disconnecting position illustrated in Fig. l to a clutch engaging,position-)wherein theinternal splines of .thecollar Ajointly mesh ywith ithe :teeth onv the .externally splined extension.82,.and.;the jawfclntch teeth,=83.

' Opposite ends of the countershaftelement `79 ,are rotatively supportedupon the` inner races of ball `bearing units 85 and 86. .The outer races of these ball bearing unitsare disposed incoaXiaLopposite end Wall openings 87...and..8,8 of the casingSS. Aradially projectingforce reactionelement 89,for.rned on..an.intermediate .portion of the-.shaftelement -79.prevents endwise movementof thegear 73 by/forceexerted by a helical expansion spring 911 -for 'therslip clutch 75. Onef'end of the vspring 91 presses againstrthefslip clutch .element`77 for impositively pressing Vdiarrletrica'lly oppositecuniform endwise projecting teeth .92 thereoninto respective notches v93 Yin theelernent. 'Onelpairofthese teeth 9.2 and notches 93is. shown'in 'detail in'Fig.'3. The vleft end of ,the-expansion spring 91 reacts against a spring cap 94 of which the `hub pressesgagainst'the.inner race of the ball bearing nnit85"which-in'turn reacts against a detachable vforce reaction element lin'the'form of a nut -9S turned upon a threaded'end portion 96 of the countershaft element 79. Thus the Adetachable 'force reaction element v95 reacts against the Vthrust ofthe spring x91 without any component of the thrust forcefbeing exerted through the balls of the ball bearingvunit 85.

-Engagementofthe disconnectable Vclutch-81 is Vcontrolled byashifter fork'97 ofwhich the shank isattached to..an`d constrained "for rotationfwith a vertical shaft V98. Furcations .1101 andf102 ofthe shifter fork-97 straddle thecollar'84I and support shifter rollers r103 -which -project into a circumferential :groove 104 Vof suchcollar. A detentrdevice105 .cooperatesrwithspaced notches `106 in the lowerffurcation 102, one ofsuch notches beingrshown to jbe ,impositively retaining the shifter fork 97 in the positiongfor releasing' the .clutch 81- or in the vclutch Vdisengagingzposition. An. upper .end portion. of. the. clutch control :shaft 9.8 has `an arm .107 .connectedtherewith for imparting rotational -movement thereto. A 1ink.108 pivotally., connects between Lthe free end1of the arm 107.I and an arm 109 projecting radially from the hub .111 ,ofia control lever,.112 for theclutch 81 vof the -auxiliary transmission unit. Lever hub 111 ispivotally supported upon a. shaft= 113 which in'turn is rotatively supported in a bearing 114 of..a bracket 115 andin ybearings 11-6 and 117.of a bracket 118. @BracketllS is .securedato the uppenplate 119 of the gear .boxby bolts 121, whereas the bracket 118 is secured to said cover plate by bolts 122.

Arcontrol lever 123 for controlling the positionof the shiftable transmissionrgear 36 yis mounted -on .and constrained 'for rotation with the shaft..113 as isa shifter arm 124 Aof whchthe lower endis disposed withina notch 125 of va .shifter railv126. rSaid shifter, rail is supported for endwisefrnovement by bearings 127 .of which one is shown in Fig". .1. .A shifter fork.128 .dependingfrom the rail 126 .cooperates with a.=groove129. in. the hub ofthe gean .for.:shifting;said.5gear.

An interlock device 131 is disposed between ,the two control levers 112 and 123 for preventing engagement of the clutch 81 in the auxiliary transmission unit excepting when the change-speed transmission gear 36 and clutch element 37 associated therewith are in the neutral position, that is, when the gear 36 is demeshed from the gear 52 and the clutch element 37 is demeshed from the clutch element 38. This device comprises a cylindrical member 132 slidable axially within a bore 133 in the bracket 115, said cylindrical member having conical end portions 134 and 135 respectively receivable by conical recesses 136 and 137 respectively within curved faces 138 and 139 carried by the levers 112 and 123, said faces being curved circumferentially of the shaft 113. Each of the conical recesses 136 and 137 is disposed circumferentially of the shaft 113 in such a position as to register with the slidable locking member 132when the transmission connection controlled thereby is in the neutral or disconnected condition. Thus in Fig. 2 it can be observed that while the control lever 112 is in the position causing the auxiliary transmission clutch 81 to be disengaged the recess 136 registers with the locking member 132 and thereby permitting such locking member to be slid to the left for accommodating movement of the lever 123 for establishing either the high speed condition with the clutch 37-38 engaged or the low speed condition with the gear 36 meshed with the gear 52. While the lever 123 is in reither of the positions meshing the gear 36 or engaging the clutch 37-38, the recess 137 will be out of registry with the locking member 132 and a portion of the flat face 139 will be in registry with such locking member, retaining it in a locked position in the recess 136, preventing engagement of the auxiliary transmission clutch 81.

When the lever 123 is in neutral causing the gear 36 to be disengaged and the clutch 37-38 to be disengaged, the recess 137 will register with the locking member 132, making it possible for the lever 112 to be rocked for engaging the auxiliary transmission clutch 81, and pursuant to such rocking of the lever 112, the recess 136 will be moved from registry with the locking member incident to camming the locking member into the recess 137, and a portion of the at face 138 will be placed in registration with such locking member for retaining it in the recess 137 and preventing movement of the gear-clutch element 36-37 from its neutral position. A positive retention of the gear-clutch element 36-37 in its neutral position is obtained by a detent device 141, while a notch 142 in the shifter rail 126 receives a spring-pressed ball 143 of such device. The ball 143 is received by a rail notch 144 when the clutch 37-38 is engaged, and a rail notch 145 registers with and receives the ball 143 when the gear 36 is meshed with the gear 52. Thus the detent device cooperates with the three notches 143, 144, and 145 for impositive retention of the gear-clutch element 36-37 in each of its three axially spaced positions.

It will be observed that the auxiliary transmission unit 22 may be optionally attached to the rear wall of the nal drive casing 12 for supplementing the change-speed transmission unit 18. When the auxiliary unit 22 is disassembled from the remainder of the transmission apparatus, the nuts 57 will be loosened and such unit 22 disassociated from the change-speed transmission unit and the final drive casing by simply withdrawing such unit rearwardly incident to telescopically disconnecting the forward splined end of the long drive shaft 32 from the internally splined section of the main transmission drive shaft 25 and incident to telescopically disconnecting the forward splined end of the auxiliary-unit tubular driven shaft 63 from the internal splines of the coupling member 64. A snap ring 146 retains the splined coupling member 64 centrally associated in its coupling position between the tubular shafts 63 and 33. After the concentric shafts 32 and 63 of the auxiliary unit have been withdrawn through the rear wall opening 62 of the final drive casing, this opening will be closed by a cover plate (not shown). In the absence of the auxiliary transmission unit 22, the change-speed transmission unit 18 will operate conventionally between the main transmission drive shaft and the ring gear 15 of the nal drive mecha` msm.

The inner end portion of the drive shaft 32 for the auxiliary transmission unit 22, that is, the portion of this shaft upon which the gear 69 is disposed, has a rearward power take-off extension 151 projecting outwardly through a rear wall opening 152 wherein the bearing unit 68 is disposed. A threaded section 153 of the drive shaft 32 for the auxiliary transmission unit 22 has a nut 154 turned thereon against the inner race of the bearing unit 68 to serve complementally with a shoulder 155 of said shaft for resisting endwise movement of the shaft. An apertured cap 156 attached to the rear wall of the auxiliary transmission casing contains an annular sealing unit 157 circumscribing the shaft.

Inasmuch as the auxiliary transmission drive shaft 32 is caused to rotate at all times with the main drive shaft 25, as a constituent of the drive shaft structure Z5- 32, the rearward power take-off extension 151 will be constantly driven irrespective of which of the power trains within the main transmission unit 18 or in the auxiliary transmission unit 22 are employed for transmitting driving force to the vehicle. `Also,this power take-off extension 151 of the auxiliary transmission drive shaft will be caused to rotate when none of the aforesaid power trains is connected for the transmission of power, that is, when both the main transmission 18 and the auxiliary transmission 22 are in neutral. Therefore, this auxiliary power take-off extension 151 adapts the transmission apparatus for use upon a towing vehicle for drawing a machine therebehind requiring parts of its mechanism to be operated by power transmitted from the power takeoif extension 151, and for these parts of the machine to be operated continuously irrespective of whether the towing vehicle is at rest.

Having thus described av single preferred embodiment of the invention with the view of clearly and concisely illustrating the same, we claim:

l. A power transmission unit comprising a casing having Va wall opening; a drive shaft having an inner end portion in said casing and projecting outwardly through said opening; a driven shaft arranged concentrically with the drive shaft, said driven shaft having an inner end portion axially spaced from the inner end portion of the drive shaft and such shaft also projecting outwardly through the casing wall opening; gears respectively on and constrained for rotation with said inner end shaft portions; a countershaft journaled in the casing in parallelism with the concentric shafts and having a radially projecting force reaction element on an intermediate portion thereof and a detachable force reaction element thereon at a position spaced axially from the first element; independently rotatable countershaft gears journaled on the countershaft on opposite sides of the radially projecting element and in respective driving relation with the first recited gears, one of the countershaft gears being between said force reaction elements and having an end axially pressable against the radially projecting element which is serviceable as an element against which such one gear axially reacts, the other end of the one gear being in opposed relation with the detachable element and having a slipclutch element constrained for rotation therewith, a companion element of the slip-clutch being constrained for rotation with the countershaft, an axially expandable spring reacting between the detachable element and the companion slip-clutch element for impositively engaging the slip-clutch and thereby establishing a driving connection between the one gear and the countershaft while the one gear reacts against the radially projecting force reaction element, and clutch means for selectively establishing or--disestablishing Aa driving connection 'between i the countershaft and the other lcountershaftgear. l 2. 'The combination-set forth inclaim kv1, whereinsaid clutch means comprises -a -set of jaw clutch teethon the radially projecting -force reaction element, a set ofjaw clutch teeth on said other countershaft gear, and a toothed element `adapted for retractive advancement into 4a 'position of concurrent meshing withsaid'setsy ofclutch teeth.

-3. In a power'transmission unit; afcasing having coaxial -opposite end wall openings; anti-friction bearing units having radiallyinner andouter races of which the outer races-are respectively mounted yin said openings; a shaft havingend-portionsrespectively carried in the inner races and having a radiallyv projecting 'force' reaction element upon an intermediate portion thereof; gears journaled on the shaft at opposite sides of-said'element,one of said gears having amend-readable-axia1ly-against-said force reaction element to lpreventaxial`disp1acement-of such gear in one direction; a sljp-clutch'comprising-a jaw component on the opposite'end of Vsaid one "gear in 20 opposed spaced relation with one'of the bearing units; a companion -jaw component slidable Vaxially"ofthe-shaft but constrained for rotation therewith lat -aposition between the rst'component and the'onebearing untya spring cap slidably ontheshaft between the-companion 25 jaw component and the one bearing unit, an 'expansion spring compressed betweensaid cap-and the companion jaw component for urging the slip-clutch jaws compressed whiletheone'gear reacts against the radially projecting force @reaction lelement and the spring cap is pressed againstthef'inner race ofthe--one bearing unit, ya detachable-'foree-reaction velement on the shaft at the other end of the fbearing-inner -race toprevent axial displacement thereofrby yexpansive force'of the spring, anda releasable Clutch interposed betweensaid shaft and the other of said gears.

54. The combination set forth in claim 3, wherein the releasable clutch comprises a set of clutch teeth on the radially projecting force reaction element, a set lof jaw clutch'teeth vonthe othervofsaid gears, and a toothed element adaptedfor lretractive advancement into a position ofconcurrent-meshing with said sets of clutch teeth.

References Cited in the le of this patent HUNITED STATES yPATENTS "Germany Dec. 1, 1932 

